Fixed incorrect requirements in the kcentroid constructor. They were a

little too weak.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403682

dlib/svm/kcentroid.h

@@ -91,7 +91,7 @@ namespace dlib
             bias_is_stale(false)
         {
             // make sure requires clause is not broken
-            DLIB_ASSERT(tolerance_ >= 0 && max_dictionary_size_ > 0,
+            DLIB_ASSERT(tolerance_ > 0 && max_dictionary_size_ > 1,
                 "\tkcentroid::kcentroid()"
                 << "\n\t You have to give a positive tolerance"
                 << "\n\t this:                 " << this

dlib/svm/kcentroid_abstract.h

@@ -72,8 +72,8 @@ namespace dlib
         );
         /*!
             requires
-                - tolerance >= 0
-                - max_dictionary_size_ > 0
+                - tolerance > 0
+                - max_dictionary_size_ > 1
             ensures
                 - this object is properly initialized
                 - #tolerance() == tolerance_